Google Music now has a Trash page, where you can view recently deleted songs for up to 28 days after they've been removed from your library. You can also undelete songs from this page, or permanently delete them if you know you want them gone. Be careful, though: if you delete a song you bought on Google Play, the only way to get it back is to repurchase it. So think twice before deleting purchased music. Hit the link for more info. [Google Play Help via Google Operating System]